The mechanism and dynamics of heavy metal transport will be investigated, utilizing lipid bilayers as models for biological membranes. Initial studies will focus on the transport of mercury, methylmercury and cadmium. Our specific objectives are to: (1) determine membrane permeabilities to heavy metals and mechanisms of heavy metal transport, with emphasis on the transport of lipid-soluble complexes of metals and inorganic anions, (2) measure the partition coefficients of heavy metals in to lipid bilayers composed of different types of lipids, including acidic, zwitterionic and neutral lipids, as well as saturated and unsaturated lipids, (3) describe the effects of heavy metals on ionic permeability and conductance of lipid bilayers, with emphasis on the electroneutral transport of anions (C1- and OH-) and interactions between heavy metals and double bonds of unsaturated lipids. The transport, permeability and conductance experiments will be conducted with planar (Mueller-Rudin) bilayers formed on a plastic support separating two aqueous solutions. Mass fluxes, ionic conductances and ionic selectivities will be measured by radioisotope and electrophysiological techniques. Partition coefficients will be measured by equilibrating spherical bilayers (liposomes) with solutions containing known concentrations of heavy metals and various salts. Our preliminary results demonstrate the feasibility of the proposed research and show that Hg2 ion transport through lipid bilayers is extremely rapid and very sensitive to the C1- concentration in the bathing solution. Furthermore, the Hg transport process is electrically silent (nonconductive) and may involve transport of the neutral complex, HgCl2. The continuation of these experiments, along the lines described in this proposal, will contribute to our understanding of heavy metal transport, bioaccumulation and toxicity in plants and animals and will provide background information for future studies with biological membranes and tissues.